(1) Field of the Invention
The present invention relates to the charging of blast furnaces and particularly to the exercise of control over the flow of material from a pressurized storage hopper into a furnace. More specifically, this invention is directed to apparatus for performing the dual functions of establishing a hermetic seal in and controlling the flow of material through a conduit such as for, example, a channel via which particulate matter is delivered to the interior of a pressurized furnace. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in a shaft furnace charging installation of the "bell-less" top type as disclosed in U.S. Pat. No. 3,693,812. In this type of charging installation the furnace is provided with one or more intermediate storage hoppers which may be alternately opened to the ambient atmosphere for loading material therefrom to the interior of the pressurized furnace via a tubular discharge channel. Such furnace charging installations, as exemplified by the disclosure of U.S. Pat. No. 4,074,835, employ a pair of serially arranged "valves" between the storage hopper and the furnace. The first or upper "valve" performs a material flow control or metering function, by increasing or reducing the area of the storage hopper discharge opening and thereby assists in the achievement of a desired distribution of material on the furnace hearth. The second or lower "valve" functions to establish the hermetic seal required to permit the alternate pressurizing and depressurizing of the storage hopper. In the prior art the metering "valve," by the very nature of its function, was designed to be moved in a substantially perpendicular direction in relation to the discharge channel and could not establish a hermetic seal. The sealing valve, on the other hand, was designed and actuated so that it could not perform a material flow control function.
The requirement for a pair of serially arranged "valves," as described above, increases the cost and complexity of a blast furnace charging installation. In some instances, particularly in the case of low and medium capacity furnaces, these additional costs are deemed significant. Accordingly, there has been a desire in the art to provide a single device which could perform the dual functions of metering the flow of granular material flowing through a conduit and establishing a hermetic seal across the conduit while maintaining the high degree of reliability which has characterized installations wherein these functions were performed by separate "valves."